Hybrid proactive on-demand routing in wireless networks

ABSTRACT

Key scalability issues in the management of routing information at each node in wireless networks running a proactive routing protocol have been identified and a solution is set forth based on hybrid proactive on-demand routing with focus on the STA association information management at each MP in a WLAN mesh. A fisheye-scope-based GAB management scheme is described where the priority of an entry is the reverse of the hop count of its associated MAP/MPP from the MP, which can be easily applicable to the case of management of general routing information. For example, the GAB proposed can maintain only those entries whose associated MAPs/MPPs are two or less hops away from the MP.

RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Patent Application No. 60/891,122 filed on Feb. 22, 2007, which is hereby incorporated by reference in its entirety for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention is related to wireless networks, and, more specifically, to a new class of hybrid proactive on-demand routing protocols for wireless networks, enabling a scalable way of routing information management at each node of the network.

In a wireless network that uses a routing protocol to direct packets or frames between nodes through multiple hops, e.g., Internet Engineering Task Force (IETF) mobile ad hoc network (MANET) and IEEE 802.11 wireless LAN (WLAN) mesh network, the management of routing information at each node is an important issue. In the case of a proactive (table-driven) routing protocol where a list of destinations and their routes are proactively maintained at each node, the issue becomes critical as the number of nodes in the network increases.

In a MANET, maintaining a huge list of destinations and their routes (typically in a table) all the time could be a problem especially for those small devices that are mobile and battery-powered. In case of WLAN mesh, the issue becomes more complicated. As shown in FIG. 1, non-mesh stations (STAs) (e.g., devices running 802.11a/b/g and non-802.11 Ethernet protocols) can participate in mesh routing indirectly through their associated mesh access points (MAPs) or mesh points collocated with portals (MPPs). Using a 6-address scheme, a MAP or an MPP can set up an end-to-end path to and/or from associated STAs that it serves as a routing proxy. (Note that inside the mesh networks, frames are relayed only through mesh points (MPs), including MAPs and MPPs, and that STAs and their addresses are not visible in this forwarding process.) For this purpose, in a proactive routing protocol (e.g., Radio Aware—Optimized Link State Routing (RA-OLSR)) each MP needs to maintain the association information of all the STAs in the network, together with a regular routing table for MPs. Because in a typical wireless mesh network the number of STAs is much bigger than that of MPs, a scalable way of handling STA association information together with MP routing information is critical, especially in large-scale deployments that could include several hundreds or even thousands of STAs.

SUMMARY OF THE INVENTION

Key scalability issues in the management of routing information at each node in wireless networks running a proactive routing protocol have been identified and a solution is set forth based on hybrid proactive on-demand routing with focus on the STA association information management at each MP in a WLAN mesh.

According to the present invention, a fisheye-scope-based Global Association Base (GAB) management scheme is described where the priority of an entry is the reverse of the hop count of its associated MAP/MPP from the MP, which can be easily applicable to the case of management of general routing information. For example, the GAB at MP5 in FIG. 1 can maintain only those entries whose associated MAPs/MPPs are two or less hops away from MP5.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned and other features and objects of the present invention and the manner of attaining them will become more apparent, and the invention itself will be best understood, by reference to the following description of a preferred embodiment taken in conjunction with the accompanying drawings, wherein FIG. 1 is a block diagram of an example of a wireless mesh network.

DESCRIPTION OF THE INVENTION

The Hybrid Proactive On-Demand Routing Protocol according to the present invention is described in detail below.

Because the management of routing information at each node in a network is more complicated and critical in a WLAN mesh network than in a MANET network due to the aforementioned issue of STA association information handling, the present invention is used on the WLAN mesh and provides a scalable way of handling STA association information at each MP under the following assumptions: (These assumptions on the association information management are based on the RA-OLSR and for description purpose only; the current invention described here is not bound to any specific routing protocol or its implementations.

-   -   Each MP (including MAP and MPP) maintains a global association         base (GAB), a table showing which STA is associated with which         MAP or MPP;     -   In addition, each MAP/MPP also maintains a local association         base (LAB), a table showing STAs that are associated with         itself; and     -   Each MAP/MPP periodically advertises the contents of its LAB to         the whole network.         Note that the GAB is a union of all the LABs in the network.

Table 1 sets forth the GAB at MP5 in FIG. 1. In principle, it should maintain the association information of all those 13 STAs in the network shown in FIG. 1 as follows (in an actual implementation, more information fields, including a sequence number, expiration/valid time and a block index for each entry, are maintained—also, the MAC addresses of the STAs are shown in Table 1 and Table 2).

TABLE 1 GAB at MP5 in FIG. 1 STA MAP/MPP STA1.1 MAP1 STA1.2 MAP1 STA1.3 MAP1 STA2.1 MAP2 STA2.2 MAP2 STA3.1 MAP3 STA3.2 MAP3 STA3.3 MAP3 STAx.1 MPP1 STAx.2 MPP1 STAx.3 MPP1 STAx.4 MPP1 STAx.5 MPP1

One way of maintaining the GAB with a limited amount of memory is to use a certain priority for each entry when updating the table: For example, a FIFO-like GAB structure where the priority of each entry is its freshness (i.e., the time when its advertisement was received) could be used.

In reality, however, a more intelligent scheme than the above example is needed, especially considering the use of on-demand routing setup procedures that will be described later. In other words, because the use of on-demand routing setup procedures in a proactive routing protocol is now unavoidable due to the limit in the size of GAB (i.e., the number of entries) at each MP, the ideal GAB management scheme should minimize (1) the use of those procedures and (2) the related response time.

Of many possibilities, the present invention provides a fisheye-scope-based GAB management scheme where the priority of an entry is the reverse of the hop count of its associated MAP/MPP from the MP. For example, the GAB at MP5 in FIG. 1 can maintain only those entries whose associated MAPs/MPPs are two or less hops away from MP5. In this case, the GAB is as follows:

TABLE 2 GAB at MP5 in FIG. 1 under fisheye-scope-based management scheme STA MAP/MPP STA1.1 MAP1 STA1.2 MAP1 STA1.3 MAP1 STA2.1 MAP2 STA2.2 MAP2 STA3.1 MAP3 STA3.2 MAP3 STA3.3 MAP3

One of the advantages of the fisheye-scope-based GAB management scheme of the present invention is that it can systematically control the use of the on-demand routing setup procedures and the response time to Route Request (RREQ) during those procedures.

Assume that every MP in FIG. 1 adopts the same policy as shown in Table 2, i.e., maintaining STA entries whose associated MAPs/MPPs are two or less hops away from it. Under this policy, we can guarantee that there is always an instant communication path between any two STAs whose MAPs/MPPs are two or less hops away from each other. On the other hand, when a source STA wants to communication with a destination STA more than two hops away, the RREQ messages generated and broadcasted by its associated MAP/MPP are responded to by those MAPs/MPPs that are two hops away from the MAP/MPP associated with the destination STA. For example, when STA2.1 wants to communicate with STAx.1, the RREQ messages generated by MAP2 can be responded to by MP7 in the middle. Note that in the on-demand routing protocol, the RREQ messages should reach and be responded to by MPP1 in the worst case, using four more hops in total.

Of course, there can be many variations of the said fisheye-scope-based STA association information management scheme. For example, one can easily think of the mixed priority of fisheye-scope and the freshness of an entry. Also, the STAs associated with MPPs connected to wired infrastructures (e.g., MPP1 in FIG. 1) can be given special priorities over other STAs when updating the association information.

Note that although the present invention relates to the issue of STA association information management in a WLAN mesh, the solution described here can be easily applicable to the general, but easier problem of management of routing information (i.e., the list (or table) of destinations and their routes) at each node in both WLAN mesh and MANET.

While there have been described above the principles of the present invention in conjunction with specific memory architectures and methods of operation, it is to be clearly understood that the foregoing description is made only by way of example and not as a limitation to the scope of the invention. Particularly, it is recognized that the teachings of the foregoing disclosure will suggest other modifications to those persons skilled in the relevant art. Such modifications may involve other features which are already known per se and which may be used instead of or in addition to features already described herein. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure herein also includes any novel feature or any novel combination of features disclosed either explicitly or implicitly or any generalization or modification thereof which would be apparent to persons skilled in the relevant art, whether or not such relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as confronted by the present invention. The applicant hereby reserves the right to formulate new claims to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom. 

1. A fisheye-scope-based routing and station association information management scheme for a multi-hop wireless network comprising routing and station association information wherein the priority of an entry is the reverse of the hop count of its associated MAP from the MP.
 2. The routing and station association information management scheme of claim 1 wherein the routing and station association information maintains only those entries whose associated MAPs are two or less hops away from the MP.
 3. The routing and station association information management scheme of claim 1 wherein there is a guaranteed instant communication path between any two STAs whose MAPs are two or less hops away from each other.
 4. The routing and station association information management scheme of claim 1 wherein, when a source STA wants to communicate with a destination STA more than two hops away, an RREQ message generated and broadcasted by its associated MAP is responded to by those MAPs that are two hops away from the MAP associated with the destination STA.
 5. The routing and station association information management scheme of claim 4 wherein the RREQ message should reach and be responded to by the MAP in no more than four hops in total.
 6. The routing and station association information management scheme of claim 1 wherein the routing and station association information entry comprises a mixed priority of fisheye-scope and the freshness of the entry.
 7. The routing and station association information management scheme of claim 1 wherein the STAs associated with wired infrastructures are given special priorities over other STAs when updating the association information.
 8. The routing and station association information management scheme of claim 1 wherein the wireless network comprises a WLAN.
 9. The routing and station association information management scheme of claim 1 wherein the wireless network comprises a node of WLAN.
 10. The routing and station association information management scheme of claim 1 wherein the wireless network comprises a MANET.
 11. A fisheye-scope-based routing and station association information management scheme for a multi-hop wireless network comprising routing and station association information wherein the priority of an entry is the reverse of the hop count of its associated MPP from the MP.
 12. The routing and station association information management scheme of claim 11 wherein the routing and station association information maintains only those entries whose associated MPPs are two or less hops away from the MP.
 13. The routing and station association information management scheme of claim 11 wherein there is a guaranteed instant communication path between any two STAs whose MPPs are two or less hops away from each other.
 14. The routing and station association information management scheme of claim 11 wherein, when a source STA wants to communicate with a destination STA more than two hops away, an RREQ message generated and broadcasted by its associated MPP is responded to by those MPPs that are two hops away from the MPP associated with the destination STA.
 15. The routing and station association information management scheme of claim 14 wherein the RREQ message should reach and be responded to by the MPP in no more than four hops in total.
 16. The routing and station association information management scheme of claim 11 wherein the routing and station association information entry comprises a mixed priority of fisheye-scope and the freshness of the entry.
 17. The routing and station association information management scheme of claim 11 wherein the STAs associated with wired infrastructures are given special priorities over other STAs when updating the association information.
 18. The routing and station association information management scheme of claim 11 wherein the wireless network comprises a WLAN.
 19. The routing and station association information management scheme of claim 11 wherein the wireless network comprises a node of WLAN.
 20. The routing and station association information management scheme of claim 11 wherein the wireless network comprises a MANET. 